Electroplating plastics

ABSTRACT

ELECTROPLATING OF A MOLDABLE PLASTIC CONTAINING A SILICEOUS FILLER IS ACHIEVED BY CONDITIONING A PREFORMED ARTICLE OF SAID PLASTIC BY A COMBINATION TREATMENT CONSISTING OF AN ACID CHROMATE ETCH AND AN HF TREATMENT AND THEREAFTER PREPLATING THE CONDITIONED ARTICLE WITH AN ELECTROLESSLY PLATABLE METAL AND ELECTROPLATING THE PREPLATED ARTICLE WITH A FINAL FINISH TO OBTAIN A METALPLATED PLASTIC PRODUCT.

tional plating processes in producing a plated product having goodadhesion of the metal plate thereto.

Such conventional plating processes involve a preplating process whichincludes cleaning; conditioning or etching the surface of the plasticwith an acid chromate solution, such as chromic-sulfuric acid, atelevated temperatures; sensitizing the surface of the plastic with anoxidizable salt, such as stannous chloride, that is absorbed and laterreduces the activator (not all conventional processes include thisstep); activating the surface with a precious metal salt, such aspalladium chloride; and electroless plating with either copper (about0.005 mil to 0.010 mil) or nickel (about 0.010 to 0.030 mil). Eachconditioning step is followed by one or more water rinses. Thecontinuous film of electrically conductive material applied by thepreplating process provides the capability for applying the final finishby conventional electrolytic processes. Following the preplate process,normal plating of copper-nickel-chrome, or nickelchrome or any of awhole variety of final finishes, including gold and silver, can beapplied by conventional electroplating techniques. For most applicationsthe final plate will be about 0.5 to 2.0 mils thick, but even thickerplate can be applied if desired.

The following procedures are representative of the conventional platingprocesses and conditions which can be used in the electroplating ofplastics in accordance with this invention.

It is to be understood that the recitation of specific plating solutionsand steps in no way limits the invention to these specific solutions andsteps. There are numerous plating systems available, and the process ofthe invention can be used with any of them, so long as an HP treatment,as herein defined, precedes or follows the acid chromate etch.

(l) Immerse in a sodium pyrophosphate cleaning solution for 2 to 5minutes at 140 F.

(2) Immerse in a sodium bisulfate neutralizing solution for to 30seconds at 75 F.

(3) Immerse in an acid chromate etching solution for 0.1 to minutes at75 to 200 F.

(4) Rinse with 5 weight percent hydrochloric acid.

(5) Immerse in a stannous chloride sensitizing solution for 15 to 60seconds at 75 F.

(6) Immerse in a palladium ammonium chloride activating solution for 15to 60 seconds at 75 F.

(7a) Immerse in an electroless copper plating solution for 5 to 30minutes at 75 F. The plating solution comprised modified Fehlingsolutions: solution A was CuSO and solution B was NaOH, NaK tartrate, NaCO and NaC H O Or (7b) Immerse in an electroless nickel plating solutionfor 5 to 30 minutes at 75 F. The plating solution usually containsnickel salts and a reducing agent such as sodium hypophosphite or aboron amine.

(8a) Strike with copper. The composition of the copper strike bath andconditions for plating were as follows:

Composition of the copper strike bath 98 gramsCuSO .5H O

15.5 millilitersConcentrated H 80 1 milliliter-UBAC Brightener No. lSufficient water to make 1 liter of solution 1 Supplied by UdyliteCorporation, Detroit, Mic

Plating conditions Voltage-2 volts DC.

Current density10 to 15 amperes/ft. Current efiiciencyl00%AnodeElectrolytic copper Temperature-75 to 80 F.

Tirne-4 to 10 minutes Agitated bath (8b) Strike with nickel. Thecomposition of the nickel strike bath and conditions for plating were asfollows:

Composition of nickel strike bath 300-410 grams-M 6H O 30-45 gramsNiCl 3/2H O 45 gramsH BO 10ml. nickel brightener N3E 1 Suflicient water tomake 1 liter of solution Supplied by Udylite Corporation, Detroit, Mich.

Plating conditions Voltage6l8 volts DC.

Current density30-80 amperes/ft. Current efficiencyl 00% Anode-Nickel(99.5%) Temperature-75-155 F. Time4l0 minutes Agitated bath Compositionof the bright copper bath 212 gramsCuSO .5H O

28.8 millilitersConcentrated H 80 4 milliliters-UBAC Brightener No. 1

75 milligramsNaCl Sufiicient water to make 1 liter of solution Platingconditions Voltage4 volts DC.

Current density30 to 40 amperes/ft. Current efficiency-98 to 100%AnodeElectrolytic copper Temperature75 to 80 F.

Time-1 to 3 minutes 1 Agitated bath 4153 minutes used in preparing thetest specimens.

' (ll) Electroplate with nickel. The composition of the nickel platingbath and conditions for plating were as follows:

Composition of the nickel plating bath 1136 gramsNiSO .6H O

312 gramsNiCl Suflicient water to make 1 gallon of solution Platingconditions Voltage4 volts DC.

Current density 40 to 50 amperes/ft. Current efficiencyto Anode-NickelTemperature-75 to 160 F. Time-30 to seconds Agitated Bath (12)Electroplate with chromium. The composition of the chrome plating bathand conditions for plating were as follows:

Composition of the chrome plating bath 350 grams-CrO 2milliliters-Concentrated H 80 Suflicient water to make 1 liter ofsolution Plating conditions Voltage6 to 8 volts DC.

Current density-90 to 110 amperes/ft.

Current efficiency20% AnodeLead Temperature80 to 140 F.

Time-30 to 90 seconds Agitation of the bath effected by the evolution ofgases Steps (1) and (2) of the conventional plating process form acleaning operation to remove any dirt or other foreign matter from thesurface of the preformed or molded object to be plated.

Step (4) of the above-described plating process is not required if theHF treatment of the conditioning step of this invention is carried outafter the acid chromate etch, and was not used in the tests made toillustrate the process of the invention. When the HF treatment iscarried out prior to the acid chromate etch in the conditioning step ofthe process of the invention, then step (4) of the conventionalelectroplating process can be utilized.

When the surface conditioned molded plastic article is to be immediatelyplated in the conventional plating process, steps (1) and (2) of theconventional plating process as described above are not required. Thus,following the conditioning treatment utilizing the combination of HFtreatment and acid chromate etch, the resulting plastic article issensitized with an oxidizable salt (5) followed by the remaining stepsas described for electroless and electroplating.

Ordinarily each conditioning and plating step is followed by one or morewater rinses.

The following specific examples are presented to further illustrate theinvention but should not be interpreted to restrict or limit theinvention.

The plastic-filler blends used in these examples were prepared byblending the indicated amounts of plastic and filler in either aBrabender Plastograph for 5 to minutes at 50 to 75 rpm. and about 370 F.in a nitrogen atmosphere or in a Banbury mixer for about 5 minutes atabout 350 F. in an air atmosphere. Compressionmolded or injection-moldedslabs having a thickness of 50 to 75 mils were prepared from the blendsand 3 /2 inch by 1% inch pieces were cut from the molded slabs for theplating tests. A precipitated hydrated silica having an average particlesize of 0.022 micron or a pumice having a particle size less than 50microns was used in the tests.

Adhesion values were determined in an adhesion test made by pulling themetal layer from the plastic or filled plastic in an Instron tester at a90 angle and at a rate of 2 inches per minute. In this test a steel bar/2-inch wide is laid down the center of the 3 /2 inch by 1% inch pieceof plated plastic and a sharp knife is used to cut through theelectroplate along each side of the bar. One end of the resulting/2-inch wide strip is pulled loose for /2 to inch. A clamp attached to awire about 2 feet long is attached to this loosened metal tab. Theplastic or filled plastic is attached to the traverse in the Instrontester and the wire to the upper jaw. The long wire is used so that theangle does not change appreciably as the metal is pulled at right anglefrom the plastic surface. The average value of the force, in pounds,required to separate the metal and plastic is multiplied by two to getthe force required per lineal inch of contact. In the specimens preparedfor this test the bright copper electroplate was 2 to 2.5 mils thick sothat the metal itself would not yield during the test. and the nickeland chromium electroplating steps were not used.

EXAMPLE I A series of plating tests was carried out utilizing anethylene/propylene copolymer containing about 3.5 weight percentethylene and 96.5 weight percent propylene which had a melt flow ofabout 1.75 dg./min. (ASTM D 1238-62T, Condition L) and a density of0.899 g./cc.

8 (ASTM D 150563T) blended with weight percent silica Conventionalelectroplating techniques, as described above, were used except that thefilled polymer was treated in a 50 weight percent aqueous solution ofammonium bifluoride following the acid chromate etch in the process ofthe invention. The following results were obtained:

Acid Total chromate etch NHiHFz treatment treat- 10 in Ad- Time, Temp.Time, Temp. time, hesion, Sample min. F. min. F. min. lb./in.

2 160 2 80 4 16 2 160 3 80 5 26 5 160 None 5 2.5

EXAMPLE 'II Plating tests were made with portions of the same filledpolymer used in Example I. Conventional electroplating techniques, asdescribed above, were used except that the filled polymer was treated ina 50 weight percent aqueous HF bath following the acid chromate etch inthe process of the invention. The following results were obtained:

Acid Total chromate etch IlF treatment treating Ad- Tnne, Temp. Tune,Temp. time, hesion Sample min. 1*. min. F. min. lb ./in

1 2 160 2 80 4 2 (control) 5 160 None 5 2. 5 30 EXAMPLE III A series ofplating tests was carried out utilizing a polypropylene which had adensity of 0.905 g./cc. and a melt flow of about 4 dg./min. blended with20 weight percent pumice. Conventional electroplating techniques, asdescribed above, were used except that the filled polymer was treated ina weight percent aqueous HF bath following the acid chromate etch in theprocess of the 40 invention. The following results were obtained:

Acid Total chromate etch HF treatment treating Ad- Tnne, Temp. Time,Temp. time, hesion, Sample min. F min. F. min. lb./in.

2 155 2 4 2.0 4 4 8O 8 2. 6 5 None 5 1 EXAMPLE IV A series of platingtests was carried out utilizing portions of the ethylene/propylenecopolymer described in Example I blended with 20 weight percent pumice.Conventional electroplating techniques, as described above, were usedexcept that the filled polymer was treated in a 50 weight percentaqueous HF bath following the acid chromate etch in the process of thisinvention. The followin g results were obtained:

an amorphous content of about 18 weight percent blended with either 10or 20 weight percent silica. Conventional electroplating techniques, asdescribed above, were used except that the filled polymer was treated ina 50 weight percent aqueous HF bath following the acid United StatesPatent ELECTROPLATING PLASTICS Johnny L. Wells, Bartlesville, Okla,assignor to Phillips Petroleum Company No Drawing. Continuation-impartof application Ser. No. 714,098, Mar. 18, 1968. This application Mar.17, 1969, Ser. No. 807,986

Int. Cl. B290 25/00; C23b 5/64 U-S. Cl. 20420 36 Claims ABSTRACT OF THEDISCLOSURE Electroplating of a moldable plastic containing a siliceousfiller is achieved by conditioning a preformed article of said plasticby a combination treatment consisting of an acid chromate etch and an HPtreatment and thereafter preplating the conditioned article with anelectrolessly platable metal and electroplating the preplated articlewith a final finish to obtain a metalplated plastic product.

This application is a continuation-in-part of Ser. No. 714,098, filedMar. 18, 1968 now abandoned.

This invention relates to the electroplating of plastics. In one aspect,this invention relates to an improved process for electroplatingplastics containing a siliceous filler. In another aspect, thisinvention relates to a method for providing electroplated plasticarticles having an improved adhesion of the metal plate thereto. In afurther aspect, there is provided a method for conditioning plasticarticles for use in an electroplating process.

BACKGROUND OF THE INVENTION The market for electroplated-plasticarticles has expanded tremendously in the last few years. Byelectroplating plastics the inherent advantages of plastics, i.e.,economy, light weight, corrosion resistance, moldability, etc., becomeavailable to both fabricators and users of electroplated parts. Presentapplications for electroplated plastics include automotive accessories(e.g., knobs, handles, trim, 'bezels), appliance parts (e.g., housings,grills, handles), plumbing fixtures (e.g., valve bodies, sink strainers,P-traps, showerheads), houseware and furniture parts (e.g., knifehandles, soap dishes, lamp bases, picture and mirror frames) andindustrial uses where the characteristics of its abrasion resistance andshielding qualities are desirable.

Although the demand for electroplated plastics has expanded, not allplastics are capable of being plated by conventional processes due tothe failure to obtain a satisfactory adhesion of the metal plate to theplastic. Thus, for example, olefin polymers have found little utility inthe formation of plated plastic articles because it has not beenpossible to obtain a strong bonding of the metal plate to the polymersurface and further because of the undesirably long time required foretching the polymer surface. Such difficulties are apparently due to thephysical and chemical properties of the olefin polymers such aspolyethylene, polypropylene, halogenated olefin polymers and the likewhich render them inert and, accordingly, unaffected by conventionaletching techniques normally employed in electroplating.

Heretofore the most widely used plastic for electroplating wasacrylonitrile-butadiene-styrene, hereinafter referred to as ABS, sinceconventional plating techniques can be employed with this plastic andthe plating bonds well. For other plastics than ABS the poor bonding ofthe plate, if formed by conventional techniques, resulted in a limiteduse of the resulting product. The necessity of having to use other thanconventional plating techniques for electroplating plastics not onlymaterially increases the cost of the electroplated product but till nowhas been unable to overcome the problem of poor bonding or adhesion ofthe metal plate so that use of such plated products has been limited tosmall parts such as knobs.

For these reasons as well as the outstanding properties possessed byother plastics and particularly the olefin polymers there has been acontinuing effort to develop a method for electroplating other plasticsby conventional techniques.

THE PRESENT INVENTION Accordingly, it is an object of this invention toprovide an improved process for metal plating plastics.

Another object of this invention is to provide a method for producing aplated plastic article having improved adhesion of the plate to theplastic surface.

A further object of this invention is to provide a process forelectroplating plastics which permits the utilization of conventionalelectroplating systems.

Another object of this invention is to provide a method for conditioningplastics so as to provide a product suitable for use in conventionalelectroplating systems.

Other aspects, objects and several advantages of this invention will beapparent to those skilled in the art from the following description andappended claims.

According to this invention there is provided a method forelectroplating a plastic which comprises the steps of:

(l) incorporating a siliceous filler in the plastic;

(2) molding the resulting plastic composition into the desiredconfiguration;

(3) conditioning the resulting molded plastic product by treating, inseries, with (a) an acid chromate etch and (b) an HP treatment;

(4) preplating the conditioned article with an electrolessly platablemetal; and

(5) electroplating the preplated article with a final finish to obtain ametal plated plastic product.

Although the overall process for electroplating plastics in accordancewith this invention utilizes the aforementioned steps, it is notessential that all the steps be performed at one time. Accordingly, onceconditioned by the HF-treating step of this invention, either alone orfollowed by an acid chromate etch step, the surface conditioned moldedplastic article can be immediately preplated or can be shipped to someother location for further processing. Thus, the HF-treating stepresults in the formation of a novel product suitable for furtherprocessing in a conventional electro lating system.

Likewise, while each step of the conditioning treatment of thisinvention is conventionally carried out immediately in sequence in oneembodiment of this invention wherein the HF treatment is utilizedfollowing the acid chromate etch treatment, the HF treated plasticarticle resulting therefrom represents a novel surface conditionedarticle which can be supplied without further treatment to operators ofconventional plating processes. This is advantageous in some instancessince it permits conventional plating processors to form plated plasticarticles without having to alter their established operations or byhaving to acquire suitable equipment for forming the HF-treated article.

Likewise, the electrolessly plated plastic article prepared by the abovesteps 1 through 4 represents a novel preplated product which, ifdesired, can be supplied in this form to a processor for electroplating.This is particularly advantageous when the final finish metal on theplastic article is to be of a type not normally utilized and thepreparation of which by the preplator would be uneconomical.

Although the process of this invention can be utilized for the platingof any moldable plastic as defined above, in one specific embodiment ofthis invention it has been found to be particularly suitable forelectroplating olefin polymers.

The term olefin polymer as used herein and in the claims is intended toinclude both homopolymers and copolymers of aliphatic l-olefins having 2to 8 carbon atoms or mixtures thereof.

The process of this invention can be utilized with any moldable plasticmaterial. As used herein and in the claims, the term plastic is intendedto include any natural or synthetic polymeric material which can bemolded into a desired final shape using heat and/or pressure. Examplesof such materials, which are listed and described in Modern PlasticsEncyclopedia for 1967, are: ABS resins, acetal resins, acrylics andmodified acrylics, alkyd resins, allyl resins, amino resins, halogenatedpolyethers, epoxy resins, fluoroplastics, furane resins, ionomers,isocyanates, nylons, parylene polymers, phenolics, phenoxy resins,polyalkenes, polycarbonates, polyesters, polyimides, polyarylene oxides,polyarylene sulfides, polysulfones, silicones, styrene polymers andcopolymers such as styrene/butadiene, vinyl polymers and copolymers,such as poly(vinyl chloride), poly(vinyl fluoride), vinylidene chloride/vinyl chloride copolymer, and the like, including blends.

The terms mold, molded, moldable, molding, and the like as used hereinand in the claims is intended to include any plastic forming processsuch as film formation by extrusion, casting, or calendering, blowmolding, injection molding, extrusion, vacuum forming, pressure forming,compression molding, transfer molding, casting, thermoforming, and thelike.

Examples of the aliphatic l-olefins are ethylene, propylene, l-butene,l-pentene, Z-methylpentene, l-hexene, 1- heptene, l-octene,1,3-butadiene, 1,4-hexadiene, 1,3-heptadiene, 1,5-octadiene, and thelike. Examples of the olefin polymers and polymer blends that can beused are polyethylene, polypropylene, poly(butene-1),poly(2-methylpentene), ethylene/ propylene copolymer, ethylene/butene- 1copolymer, ethylene/hexene-l copolymer, ethylene/propylene/1,4-hexadieneterpolymer, ethylene/propylene/ butene-l terpolymer, polyethylene/polypropylene blends, polyethylene/polypropylene/polydiene blends, andthe like.

Such polymers are known to be inert to most chemicals and whenheretofore plated formed products having poor metal to plastic adhesionvalues. This, in turn, limited the end uses of such metal plated itemsto those applications where the strength of the bond or adhesion valuewas not critical.

When carrying out the process of the present invention with an olefinpolymer there is achieved a substantial increase in the metal to plasticadhesion values of the plated article. In addition, the combinationconditioning treatment can be carried out for reduced periods, thusproviding the further advantage of reducing the overall etch timerequired to satisfactorily condition the polymer surface for plating ascompared to plating techniques heretofore known in the art.

The surface conditioning step of the present invention utilizes acombination, in series of (a) an acid chromate etch and (b) an HFtreatment. The specific sequence of these two operations is notcritical. Accordingly, the filled plastic article can be treated withthe acid chromate etch followed by the HF treatment or conversely by theHF treatment followed by the acid chromate etch. To avoid contaminationof the various treating agents the plastic article should be rinsedafter each separate treatment.

The term HF treatment as used herein and in the claims is intended tocover any treatment whereby the surface of the plastic article iscontacted with hydrogen fluoride. For convenience, aqueous solutions ofhydrofluoric acid or acid fluoride salts are employed in effecting thetreating of the surface of the plastic article with hydrogen fluoride.Examples of suitable acid salts are those of the formula MF,,.(HF)wherein M is the ammonium ion or a metal such as the alkali metals,alkaline earth metals, and the like and x is the valence of M. Suchsalts include NH HF NaHF KHF CaH F and the like, including mixturesthereof. In addition, if desired, the HF treatment can be carried out inthe vapor phase. The time required for successful treatment of theplastic article is dependent on the concentration of the HP in thetreating zone. When utilizing an aqueous hydrofluoric acid solution, theconcentration of the HF can be in the range of about 0.1 to saturation.When utilizing an aqueous solution containing a water-soluble acidfluoride salt, the concentration of the salt in the aqueous solution canlikewise be in the range of about 0.1 weight percent to saturation,preferably 1.0 to saturation.

When carrying out a vapor phase HF treatment the minimum temperaturewill be determined by that required to vaporize the HF. Thus, atemperature of at least 67 F. is used when the process is operated atatmospheric pressure, with higher temperatures being used at highertreating pressures. The maximum temperature that can be used is at least50 F. below the softening point of the plastic being treated. The HFtreatment is ordinarily carried out utilizing an aqueous solution of thetreating agent for a period of 0.1 to 10 minutes, and preferably 2 to 4minutes.

The HP treatment is normally carried out at room tem perature whenutilizing an aqueous treating agent but can be carried out attemperatures up to essentially the boiling point of the solution.Temperatures above the normal boiling point can also be used providedthe pressure is suflicient to maintain a liquid phase. Temperatures inthe range of 30 to 200 F. are suitable for the aqueous systems.

The acid chromate etch treatment is that conventionally employed inmetal plating and is normally carried out at temperatures in the rangeof F. to 200 F. The acid chromate etch treatment is generally carriedout for a period of time in the range of 0.1 to 20 minutes. However,when used in the treating of olefin polymers in accordance with thisinvention a treating time of 2 to 4 minutes is preferred.

The acid chromate etch solution is usually formed by the addition of achromate salt or CrO to a strong acid such as sulfuric acid or asulfuric acid-phosphoric acid mixture. Typical of such a solution isthat obtained by mixing the following:

(1) Concentrated H 50 K CrO at F.,

(2) H 0 (262 ml.) saturated with CrO at 80 F., and

(3) H O to make a total of 1100 ml.

The siliceous fillers which are utilized in the polymer are generallythose having a particle size of less than 50 microns and preferably lessthan 10 microns.

The filler is utilized in an amount in the range of 1-60, preferably1-30 weight percent based upon the total weight of filled plastic andfiller. All percentages recited hereinafter are on this basis. By filledplastic is meant that portion of a plastic molding into which the fillerhas been incorporated. The filler or mixtures thereof can beincorporated into the plastic by any known technique using the knownmilling and blending equipment, such as a Banbury mixer, a BrabenderPlastograph, and the like.

Examples of suitable siliceous fillers are the synthetic silicas andhydrated silicas, and naturally-occurring minerals having a highi.e.,greater than about 70 weight percent-silica content, such as pumice,diatomaceous earth, and the like, including mixtures thereof.

As indicated, it would be highly desirable in the electroplating of aplastic article to be able to utilize conven- (238 ml.) saturated withchromate etch in the process of the invention. The following resultswere obtained:

copolymer containing about 43 weight percent ethylene and 57 weightpercent propylene and having a Mooney 4 Amorphous polypropylene wasdetermined by the following xylenes solubility test: 0.95 g. of polymerwas mixed with 95 ml. mixed xylenes, heated for minutes at 285 F.,cooled, and centrifuged. The solvent was evaporated from a 25-ml.aliquot of the supernatant liquid, the residue was weighed, and theweight was multiplied by 400.

EXAMPLE VI A series of plating tests was carried out as in Exampleviscosity (ML-4 at 212 F., ASTM D164663) of 45, blended with weightpercent silica. Conventional elec- V utilizing a similar polypropylenehaving a melt flow of tfoplating ltichniques, as described abOW, Wereused 12.4 dg./min. and an amorphous content of about 19 weight percent.The following results were obtained;

cept that the filled polymer was treated in a weight percent aqueous HFbath', following the acid chromate Acid chromate etch Time, Temp., min.F.

HF treatment Total treating time,

Time, Temp.,

' F. min.

4 5 (control).

EXAMPLE VIII A series of plating tests was carried out utilizing apolymer blend containing 80 weight percent of a polypropylene having adensity of 0.905 g./cc. and a melt flow of about 4 dg./min., 10 weightpercent of a polyethylene having a density of 0.960 g./cc. and a meltindex of 0.1 dg./min., and 10 weight percent of an ethylene/ propyleneTotal Acid chromate etch HF treatment treatmg Ad- SiOg, wt. Time, Temp,Time, Temp., time hesion, Sample percent min. F. min. F. min. lb./1n

1 10 2 155 2 S0 4 17. 0 2 10 5 155 2 7 15. 0 3 (control) 10 5 None 5 1 420 2 155 2 80 4 30.0 5 20 5 155 2 80 7 12.0 6 (control). 20 5 155 None 51 7 (control)- 0 2 155 2 80 4 0. 9 8 (control)- 0 5 155 2 80 7 0. 9

EXAMPLE VII etch 1n the process of the inventlon. The following resultswere obtained:

Acid chromate etch HF treatment Total treating Adhe- Time, Temp., Time,Temp., time, sion, Sample min. F. min. F. min. lb./in.

1 0. 5 155 0. 5 80 1 4. 0 2 1 155 1 80 2 4. 0 3 2 155 2 80 4 7. 0 4- 4155 4 80 8 7. 0 5 (control) 4 155 None 4 1 EXAMPLE IX A series ofplating tests was carried out utilizing a polyethylene having a meltindex of 5 dg./min. and a density of 0.960 g./cc. blended with 20 weightpercent silica. Conventional electroplating techniques, as describedabove, were used except that the filled polymer was treated in a 50weight percent aqueous HF bath following the acid chromate etch in theprocess of the invention. The following results were obtained:

ventional electroplating techniques, as described above, were usedexcept that the filled polymer was treated in a 50 weight percentaqueous HF bath before the acid chromate etch in the process of theinvention. The following results were obtained:

A series of plating tests was carried out utilizing portions of the samefilled polymer used in Example I. Conventional electroplatingtechniques, as described above, were used except that the filled polymerwas treated with HF vapor following the acid chromate etch in theprocess of the invention. The following results were obtained:

Acid chromate etch HF treatment In Examples IX electroplating steps (7b)and (8b) were usedi.e., a nickel electroless step Was followed by anickel strike. In Example XI, electroplating steps (7a) and (8a) wereusedi.e., a copper electroless step was followed by a copper strike.

EXAMPLE XII A further series of plating tests was carried out utilizingportions of an ethylene/propylene copolymer (Marlex 9600) containing 3weight percent ethylene and having a melt fiow of 4.2 dg./min. and adensity of 0.898 g./cc. blended with silica (HiSil404). Conventionalelectroplating techniques, as described above, were used, except thefilled polymer was (1) treated for 2 minutes at 155 F. with an acidchromate etch solution consisting of 283 ml. water, 45 g. chromiumtrioxide, 918 ml. sulfuric acid (96%), 300 ml. phosphoric (85%) and 0.2gram wetting agent and thereafter (2) treated with an aqueous HF orammonium bifluoride (NH HF bath at an HP or ammonium bifluorideconcentration as indicated below. Adhesion was determined following theelectro plating of a nickel strike and bright copper (Step 10 supra).The following results were obtained.

EXAMPLE XIII A further series of plating tests was carried out utilizingportions of the same polymer and same silica filler used in Example XII.Fifty parts by weight of polymer were blended with 50 parts by weight offiller in a Brabender Plastograph at 195 C. for six minutes in anitrogen atmosphere. Compression-molded samples were plated in the samemanner as in Example XII using a portion of the same acid chromate etchsolution at the same temperature F.) in etch step (1), and using anaqueous solution containing 25 Weight percent ammonium bifluoride at thesame temperature used in Example XII (room temperature) for two minutesin etch step (2). Adhesion was determined in the same manner as inExample XII. The following results were obtained:

The above clearly demonstrates that substantially improved adhesion isachieved for the metal platings when the combination etch system isemployed.

From the foregoing examples it can be seen that utilization of thecombination treatment consisting of an acid chromate etch and an HPtreatment for the conditioning of a moldable plastic article containinga siliceous filler therein results in the obtaining of a metal platedproduct having improved adhesion.

In addition, the examples clearly demonstrate that utilization of theconditioning treatment of the present invention permits the satisfactoryplating of a plastic ar ticle in conventional metal plating processes.

Reasonable variations and modifications of this invention can be made,or followed, in view of the foregoing disclosure, without departing fromthe spirit or scope thereof. a

I claim:

1. A process for electroplating a moldable plastic which comprises thesteps of (l) incorporating a siliceous filler into said plastic;

(2) molding the resulting composition of plastic and filler;

(3) conditioning the molded plastic product of step (2) by contactingwith a combination, in series, of (a) an acid chromate etch and (b) anHP treatment;

(4) preplating the resulting conditioned product of step (3) with anelectrolessly platable metal; and

(5) electroplating the preplated product of step (4) with a final finishto obtain a metal-plated plastic product.

2. A process according to claim 1 wherein the molded product of step (2)is washed prior to conditioning with the combination treatment of step(3).

3. A process according to claim 1 wherein the molded product of step (2)is conditioned by contacting first with an acid chromate etch (a) andthen with the HF treatment (b).

4. A process according to claim 1 wherein the molded product of step (2)is conditioned by first carrying out the HF treatment (b) followed bythe acid chromate etch (a).

5. A process according to claim 1 wherein said plastic is an olefinpolymer.

6. A process according to claim 1 wherein said siliceous filler ispresent in an amount in the range of 1 to 60 weight percent.

7. The product of the process of claim 1.

8. A process according to claim 1 wherein said acid chromate etch iscarried out utilizing a mixture of phosphoric acid and sulfuric acid.

9. A process for conditioning a molded plastic product having asiliceous filler incorporated therein so as to render same susceptibleto electroplating which comprises treating said molded plastic productwith a combination in series of (a) an acid chromate etch and (b) an HFtreatment.

10. A process according to claim 9 wherein said molded plastic productis washed prior to conditioning.

11. A process according to claim 9 wherein said molded product isconditioned by first treating with (a) an acid chromate etch and (b) anHF treatment.

12. A process according to claim 9 wherein said molded product isconditioned by treating with (b) an HF treatment and then (a) an acidchromate etch.

13. A process according to claim 9 wherein said plastic is an olefinpolymer.

14. The conditioned molded plastic product of the process of claim 9.

15. A process for electrolessly preplating a moldable plastic whichcomprises the steps of:

(1) forming a composition of said plastic having a siliceous fillertherein;

(2) molding the resulting siliceous filler containing plasticcomposition;

(3) conditioning the molded product by treating, in series, with (a) anacid chromate etch, and (b) an HP treatment; and

(4) thereafter preplating the resulting conditioned molded plasticproduct with an electrolessly platable metal.

16. A process according to claim 15 wherein the molded product of step(2) is washed prior to conditionmg.

17. A process according to claim 15 wherein said molded plastic productis conditioned by first treating with (a) an acid chromate etch and then(b) an HP treatment.

18. A process according to claim 15 wherein said molded plastic productis conditioned by first treating with (b) an HP treatment and then (a)an acid chromate etch.

19. The electrolessly preplated plastic product of the process of claim15.

20. The process of claim 15 wherein said plastic is an olefin polymer.

21. A process for preplating a filled plastic which comprises the stepsof:

(1) conditioning a molded product of said filled plastic having asiliceous filler therein by treating with a combination in series of (a)an acid chromate etch and (b) an HF treatment and (2) thereafterpreplating the resulting conditioned product with an electrolesslyplatable metal.

22. A process according to claim 21 wherein said molded product iswashed prior to conditioning.

23. A process according to claim 21 wherein said molded product isconditioned by contacting first with (a) an acid chromate etch and then(b) an HP treatment.

24. A process according to claim 21 wherein said molded product isconditioned by contacting first with (b) an HP treatment and then (a) anacid chromate etch.

25. The process of claim 21 wherein said plastic is an olefin polymer.

26. A process for electroplating a moldable plastic which comprises thesteps of:

(1) conditioning a preformed product of said plastic having 1 to 30weight percent of a siliceous filler therein by treating said productwith a combination, in series, of (a) an acid chromate etch, and (b) anHP treatment;

(2) preplating the resulting conditioned product with an electrolesslyplatable metal; and

(3) electroplating the resulting preplated product with a final finishto obtain a metal-plated plastic product.

27. A process according to claim 26 wherein said molded product iswashed prior to conditioning.

28. A process according to claim 26 wherein said molded product isconditioned by treating first with (a) an acid chromate etch and then(b) an HF treatment.

29. A process according to claim 26 wherein said molded product isconditioned by treating first with (b) an HP treatment and then (a) anacid chromate etch.

30. A process according to claim 26 wherein said plastic is an olefinpolymer.

31. A process for conditioning a molded article formed of a moldableplastic having a siliceous filler therein which comprises contacting thesurface of said article with an HF treating agent.

32. A process according to claim 31 wherein said HF treating agent isselected from the group consisting of aqueous hydrofluoric acid having aconcentration of at least 0.1 weight percent HF and an aqueous solutionof a water soluble acid fluoride salt having a concentration of at least0.1 Weight percent salt therein.

33. A process according to claim 31 wherein said plastic is an olefinpolymer.

34. The HF-treated product of the process of claim 31.

35. A process for electroplating a plastic containing a siliceous fillerwhich comprises conditioning said plastic by contacting with acombination, in series, of (a) an acid chromate etch and (b) an HPtreatment and thereafter plating the resulting conditioned plastic byfirst preplating with an electrolessly platable metal and thereafterelectroplating the resulting preplated plastic.

36. A process for conditioning a plastic having a siliceous fillerincorporated therein so as to render said plastic susceptible toelectroplating which comprises treating said plastic product with an HFtreatment.

References Cited UNITED STATES PATENTS 1,482,793 2/ 1924 Hartmann 15'62X2,923,651 2/1960 Petriello 154-80 3,305,460 2/ 1967 Lacy 204-203,347,724 10/1967 Schneble et al. 156--151 3,396,046 8/1968 Landau11747X 3,429,788 2/ 1969 Parstorfer 204-30 3,466,232 9/1969 Francis etal. 204-30 3,434,867 3/1969 Rousselot 11747 OTHER REFERENCES CondensedChemical Dictionary, 7th edition, Reinhold, September 1966, p. 842.

HOWARD S. WILLIAMS, Primary Examiner US. Cl. X.R.

